function main() {
	var canvas = document.getElementById("example");
	if(!canvas){
		console.log('Failed to retireve the <canvas> element');
		return;
	}
	
	var ctx = canvas.getContext('2d');
	
	// Draw a blue rectangle
	ctx.fillStyle = 'rgba(0,0,255,0.5)';
	ctx.fillRect(120,10,150,150)
}
